OLED display devices belong to the currently mainstream display devices and have the advantages of self-luminous property, wide viewing angle, rapid response speed, stable image, high brightness, rich color, high resolution, low driving voltage, low energy consumption, etc.
An OLED display device mainly comprises a thin-film transistor (TFT) array substrate and organic light-emitting diodes (OLEDs) disposed on the TFT array substrate. An OLED generally includes a lamination structure by a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL) and a cathode in sequence. An electron injection layer (EIL) may also be disposed between the ETL and the cathode.
In the manufacturing process of the OLED, the above layers are evaporated on a base substrate in sequence, and the inclusion of foreign particle may be caused. The foreign particle will affect the injection and recombination of holes and electrons, and hence a region containing the foreign particle will not emit light. Thus, the problem of black spots in pixels may be caused, and the product yield can be reduced. Because an OLED is a self-luminous device, once the layers are mixed with impurities, it is difficult to repair the OLED. The OLED display has to be dropped if the display quality is severely affected, and hence the rise of cost can be caused.